It's not perfect, but The Simpsonsis the funniest animated film in years, writes Donald Clarke

Directed by David Silverman. Voices of Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith, Hank Azaria, Harry ShearerPG cert, gen release, 87 min

THE gap between the delivery of the Ten Commandments to Moses and the release of Cecil B DeMille's movie spin-off seems to have been in the order of 4,000 years. It might, therefore, be something of an exaggeration to describe The Simpsons Movieas the most eagerly awaited film of all time. Still, in the 17 years since television's yellowest family first secured their own show, Greater Springfield - that is to say, the world - has been alive with speculation concerning an expansion into cinemas. The longer the wait has gone on, the greater the fear of disappointment has become. Could something so delightfully familiar still provide the basis for a feature-length film? Cinemas have, until today, been some of the few places you can not encounter The Simpsons. It is, in some respects, like making a film based on the weather or on traffic.

First things first. The Simpsons Movieis the most amusing American animated feature to come our way since The Incredibles. Centring on an environmental catastrophe precipitated by Homer dumping pig excrement into Lake Springfield, the picture finds time to take its customary cracks at organised religion, corporate irresponsibility and the fatuousness of the news media. As ever before, the script seamlessly melds lowbrow slapstick with dense cultural references to provide an entertainment that should prove equally diverting for dunderheads and boffins. Watch as Homer crashes through the roof before a surprised Grandpa. Elsewhere, enjoy Lisa, still annoyingly sanctimonious, boring Springfield to death with an environmental presentation entitled An Irritating Truth. A horse would have trouble sitting through this film without laughing.

And yet. There is something a tiny bit disappointing about The Simpsons Movie. For a start, unlike the guys behind South Park, who knocked the ball out of the park with their film, Matt Groening and his writers have failed to find something properly cinematic to do with their characters here. The lynch mob that gathers to tear Homer limb from limb does fill the wide screen nicely - Bumblebee Man, Disco Stu and Sideshow Mel are all there - and the scenes in Alaska are satisfactorily epic, but the picture never feels like anything other than an extended episode of the series.

There is, moreover, a worrying tendency towards sentimentality in the script. The first act finds Homer making friends with a pig just as Bart is getting on good terms with Ned Flanders. While the Simpson paterfamilias snuggles up to his porcine chum and ignores his son's personal traumas, Ned Flanders demonstrates the right way to bring up a child.

What is going on here? A key early line in the series sees Homer comforting the kids after a characteristic disaster. "You tried your best and you failed miserably," he says. "The lesson is 'never try'." The first few series of the show, like those of its near contemporary Seinfeld, stuck closely to the "No hugging. No learning" principle. The elevation of Ned to the status of role model demonstrates a worrying drift away from cynicism.

For all that, The Simpsons Movie, when viewed in isolation, remains a delightful piece of work. The bedlamites who decided to allow Mr Burns only a couple of lines should be dispatched forthwith to the nearest alienist, but the picture still buzzes with invention and mischievous intelligence. If nothing else, the fans will want to go and see which resident of Springfield gets killed in the last few frames. Could it be Lisa's new Irish boyfriend Colin? After hearing his ghastly singsong "brogue", most domestic viewers will wish it so.